Thin film transistor array and EL display employing thereof

ABSTRACT

EL display has a luminescence unit having a luminescence layer being disposed between a pair of electrodes and a thin film transistor array unit controlling luminescence of the luminescence unit. An interlayer insulation film is disposed between the luminescence unit and the transistor array unit. An anode of the luminescence unit is connected electrically to the thin film transistor array via a contact hole of the interlayer insulation film. The thin film transistor array further has a current supplying relaying electrode that is connected to the anode of the luminescence unit via the contact hole of the interlayer insulation film. A diffusion prevention film is formed on the boundary face of the anode of the luminescence unit and the relaying electrode.

RELATED APPLICATIONS

This application is a Continuation of International Application No.PCT/JP2012/007516, filed on Nov. 22, 2012, which in turn claims thebenefit of Japanese Application No. 2012-006693, filed on Jan. 17, 2012,the disclosures of which Applications are incorporated by referenceherein.

TECHNICAL FIELD

The present disclosure relates to a TFT (Thin Film Transistor) arrayunit and an OLED (Organic Light Emitting Device) display employing sucha TFT array unit.

BACKGROUND

TFTs have been employed in driving circuits of display devices such asOLED displays and LCD displays, and are being developed for improvingtheir characteristics. Emergence of large-sized and high definitiondisplays require these TFTs to have large current driving performance.Recently, TFT made of a crystallized semiconductor film, e.g.polycrystalline silicon or micro crystallite silicon, as an active layeris attracting attention.

As crystallization process for semiconductor films, high temperatureprocess using temperature of 1000 degrees Celsius or more has beenestablished. Recently, low temperature process using temperature of 600degrees Celsius or less is being developed. The low temperature processcan reduce manufacturing cost because this process does not require ause of expensive substrate such as quartz having an excellent heatresistance.

The laser annealing which uses a laser beam for heating attractsattention as one method of the low temperature process. In this method,a laser beam is irradiated on a non single crystal semiconductor film(amorphous silicon or polycrystalline silicon) which is formed on aheat-resistant insulating substrate such as glass substrate, and thesemiconductor film is melted as a result. The semiconductor film is thencrystallized during a cooling process. Using this crystallizedsemiconductor film as the active layer (channel domain), TFT is formedintegrally. The crystallized semiconductor film has a high mobilitycarrier, and this improves the performance of TFTs.

As the structure of these TFTs, a bottom-gated structure having a gateelectrode disposed under a semiconductor layer is mainly used. JapanesePatent Application Publications JP2001-028486A1 and JP2009-229941A1describe the examples of such TFTs.

JP2001-028486A1 describes a method of first forming a wiring (electrode)connected to a transistor on a substrate, and then forming a planarizedinsulation film (an interlayer insulation film) made of photosensitivepolyimide by spin coat method so that the film covers the wiring(electrode). Next, a connection hole (contact hole) is formed on theplanarized insulation film using lithography method. An organic ELdevice, which is being connected to the wiring through the connectionhole, is then formed on the planarized insulation film.

JP2009-229941A1 describes a protective insulation film layered on asecond metal layer (electrode) and a planarized insulation film (aninterlayer insulation film) layered on the protective insulation filmeach having a contact hole for inserting a connecting contact whichelectrically connects the second metal layer and an anode electrode(lower electrode). The contact hole has a cone-shape that is convexeddownward so that the inner surfaces of the protective insulation filmand the planarized insulation film are connected without a step.

SUMMARY

An EL display of the present disclosure includes a luminescence unithaving a luminescence layer being disposed between a pair of electrodes;a thin film transistor array unit controlling the luminescence of theluminescence unit; an interlayer insulation film disposed between theluminescence unit and the transistor array unit; and a current supplyingelectrode connected electrically to an electrode of the luminescenceunit and for connecting the electrode of the luminescence unit to thethin film transistor array via a contact hole of the interlayerinsulation film. Further, a diffusion prevention film is formed on theboundary face of the electrode of the luminescence unit and the currentsupplying electrode. The diffusion prevention film is made of an oxidehaving a main component same as the material constituting the electrodeof the luminescence unit.

A thin film transistor array unit of the present disclosure, which hasan interlayer insulation film disposed between a luminescence unit andhas a current supplying electrode connected electrically to an electrodeof the luminescence unit via a contact hole of the interlayer insulationfilm, forms a diffusion prevention film on the boundary face of theelectrode of the luminescence unit and the current supplying electrode.The diffusion prevention film is made of an oxide having a maincomponent same as the material constituting the electrode of theluminescence unit.

The foregoing structure allows satisfactory of both electric contactcharacteristic and reduction of counter diffusion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective diagram of an EL display according to anexemplary embodiment.

FIG. 2 is a perspective diagram illustrating an example of a pixel bankof the EL display according to the exemplary embodiment.

FIG. 3 is an electrical circuit diagram illustrating a circuit structureof a pixel circuit of a TFT according to an exemplary embodiment.

FIG. 4 is a front view illustrating a structure of a pixel of a TFTaccording to an exemplary embodiment.

FIG. 5 is a sectional view along 5-5 line of FIG. 4.

FIG. 6 is a sectional view along 6-6 line of FIG. 4.

FIG. 7A is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 5 according to an exemplaryembodiment.

FIG. 7B is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 5 according to the exemplaryembodiment.

FIG. 7C is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 5 according to the exemplaryembodiment.

FIG. 7D is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 5 according to the exemplaryembodiment.

FIG. 7E is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 5 according to the exemplaryembodiment.

FIG. 7F is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 5 according to the exemplaryembodiment.

FIG. 8A is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 6 according to an exemplaryembodiment.

FIG. 8B is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 6 according to the exemplaryembodiment.

FIG. 8C is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 6 according to the exemplaryembodiment.

FIG. 8D is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 6 according to the exemplaryembodiment.

FIG. 8E is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 6 according to the exemplaryembodiment.

FIG. 8F is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 6 according to the exemplaryembodiment.

FIG. 8G is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 6 according to the exemplaryembodiment.

FIG. 8H is a sectional view illustrating a manufacturing process of aportion of the TFT array unit shown in FIG. 6 according to the exemplaryembodiment.

FIG. 9A is a sectional view illustrating a manufacturing process of aportion corresponding to the area A of FIG. 6.

FIG. 9B is a sectional view illustrating a manufacturing process of theportion corresponding to the area A of FIG. 6.

FIG. 9C is a sectional view illustrating a manufacturing process of theportion corresponding to the area A of FIG. 6.

FIG. 9D is a sectional view illustrating a manufacturing process of theportion corresponding to the area A of FIG. 6.

FIG. 9E is a sectional view illustrating a manufacturing process of theportion corresponding to the area A of FIG. 6.

FIG. 9F is a sectional view illustrating a manufacturing process of theportion corresponding to the area A of FIG. 6.

FIG. 9G is a sectional view illustrating a manufacturing process of theportion corresponding to the area A of FIG. 6.

DETAILED DESCRIPTION

A TFT array unit and an EL display employing this unit according to oneembodiment are described with reference to FIGS. 1 to 8.

As illustrated in FIGS. 1 to 3, the EL display comprises: TFT array unit1; anode 2, EL (Electro Luminescence) layer 3, cathode 4 (upperelectrode) that are layered in sequence. TFT array unit 1 includesmultiple TFTs. Anode 2 is a lower electrode. EL layer 3 is a lightemitting layer made of organic material. Cathode 4 is a transparentupper electrode. Anode 2, EL layer 3, and cathode 4 are collectivelycalled “luminescence unit” hereafter. The luminescence unit iscontrolled by TFT array unit 1.

The luminescence unit has the following structure: EL layer 3 isdisposed between a pair of electrodes (the anode 2 and cathode 4); ahole-transport layer is layered between anode 2 and EL layer 3; and anelectron-transport layer is layered between EL layer 3 and a transparentcathode 4. TFT array unit 1 has multiple pixels 5 aligned in matrix.

Each of the pixels 5 is controlled by pixel circuit 6 which are providedin each of the pixels 5. TFT array unit 1 has multiple gate wirings 7,source wirings 8, and power supply wirings 9. Gate wirings 7 are alignedin row. Source wirings 8 function as signal lines and are aligned incolumn so as to intersect gate wirings 7. Although not shown in FIG. 1,power supply wirings 9 extend in parallel to source wirings 8.

Each of pixel circuits 6 has TFT 10 working as a switching device andTFT 11 working as a driving device. One gate wiring 7 is connected tomultiple gate electrodes 10 g of TFTs 10 that are aligned in a same row.One source wiring 8 is connected to multiple source electrodes 10 s ofTFTs 10 that are aligned in a same column. One power supply wiring 9 isconnected to multiple drain electrodes 11 d of TFTs 11 that are alignedin a same column.

As illustrated in FIG. 2, each of pixels 5 of the EL display has subpixels 5R, 5G, and 5B in three colors (red, green, blue) which areformed on a display surface and are aligned in matrix (sub pixels 5R,5G, 5B are referred to simply as “sub pixels” hereafter). Each of thesub pixels is separated from each other by bank 5 a. Bank 5 a is formedby a first group of protrusions parallel to gate wirings 7 and a secondgroup of protrusions parallel to source wirings 8 crossing each other.Each of the sub pixels is formed in an area surrounded by theseprotrusions, in other words, in an opening of bank 5 a.

Anodes 2 are formed on an interlayer insulation film of TFT array unit 1and in the openings of bank 5 a for every sub pixels. EL layers 3 areformed separately on anodes 2 for every sub pixels. The transparentcathode 4 is formed continuously so as to cover bank 5 a and to commonlycover all of the sub pixels and EL layers 3 of the EL display.

TFT array unit 1 has pixel circuits 6 that are provided for every subpixels. Each of the sub pixels and corresponding pixel circuit 6 iselectrically connected by a contact hole described later and a relayelectrode.

As illustrated in FIG. 3, pixel circuit 6 has TFT 10 working as aswitching device, TFT 11 working as a driving device, and capacitor 12storing data for displaying image.

TFT 10 has gate electrode 10 g connected to gate wiring 7; sourceelectrode 10 s connected to source wiring 8; drain electrode 10 dconnected to capacitor 12 and gate electrode 11 g of TFT 11; and asemiconductor film (not illustrated). When a voltage is applied to gatewiring 7 and source wiring 8, capacitor 12 is charged with the voltageapplied to source wiring 8 as display-data.

TFT 11 has gate electrode 11 g connected to drain electrode 10 d of TFT10; drain electrode 11 d connected to power supply wiring 9 andcapacitor 12; source electrode 11 s connected to anode 2; and asemiconductor film (not illustrated). TFT 11 supplies current, whichcorresponds to amount of voltage stored in capacitor 12, to anode 2 viasource electrode 11 s using power supply wiring 9. As discussed above,the EL display according to this embodiment employs an active matrixmethod that controls the display of images for every pixel 5 positionedon the intersections of gate wirings 7 and source wirings 8.

Next, a structure of a pixel constituting TFT array unit 1 is describedwith reference to FIGS. 4 to 6.

As illustrated in FIGS. 4 to 6, pixel 5 is made by a layered structurecomprising: substrate 21; first metal layer 22 which is an electricconduction layer; gate insulation film 23; semiconductor films 24 and25; second metal layer 26 which is an electric conduction layer;passivation film 27; electric conduction oxide film 28 configured by ITOfor example; and third metal layer 29 which is an electric conductionlayer.

First metal layer 22 is layered on substrate 21. Gate electrode 10 g ofTFT 10 and gate electrode 11 g of TFT 11 are formed in first metal layer22. As discussed later, the gate electrode 10 g of TFT 10 and gateelectrode 11 g of TFT 11 are formed from the first metal layer 22. Gateinsulation film 23 is formed on substrate 21 and first metal layer 22 soas to cover gate electrodes 10 g and 11 g.

As shown in FIGS. 4-6, semiconductor film 24 is disposed on gateinsulation film 23 (between the film 23 and second metal layer 26) andon an area that overlaps with gate electrode 10 g. Similarly,semiconductor film 25 is disposed on gate insulation film 23 (betweengate insulation film 23 and second metal layer 26) and on an area thatoverlaps with gate electrode 11 g.

As shown in FIGS. 5-6, second metal layer 26 is formed on the films 23,24 and 25. Source wiring 8; power supply wiring 9; and electrodes of TFT10 (source electrode 10 s, drain electrode 10 d), and electrodes of TFT11 (source electrode 11 s, and drain electrode 11 d) are formed insecond metal layer 26. As discussed later, wiring 8, power supply wiring9, electrodes of TFT 10 and electrodes of TFT 11 are formed from themetal of the second metal layer 26.

The electrodes 10 s and 10 d are formed such that each of them overlapswith a portion of semiconductor film 24 at where these electrodes faceeach other. Source electrode 10 s is formed extending from source wiring8 which is on second metal layer 26.

Similarly, the electrodes 11 d and 11 s are formed such that each ofthem overlaps with a portion of semiconductor film 25 at where theseelectrodes face each other. Drain electrode 11 d is formed extendingfrom power supply wiring 9 which is in second metal layer 26.

TFT 10 is a bottom gate type transistor which has gate electrode 10 gformed on a lower layer of source electrode 10 s and drain electrode 10d. Similarly, TFT 11 is a bottom gate type transistor which has gateelectrode 11 g formed on an upper layer of source electrode 11 s anddrain electrode 11 d.

Gate insulation film 23 has contact hole 30 penetrating the film 23 in athickness direction at where the film 23 overlaps with drain electrode10 d and gate electrode 11 g. Drain electrode 10 d is connectedelectrically to gate electrode 11 g, which is formed on first metallayer 22, via contact hole 30.

As shown in FIGS. 5-6, passivation film 27 is formed on gate insulationfilm 23 and second metal layer 26 such that passivation film 27 coversthe source electrodes 10 s, 11 s and drain electrodes 10 d, 11 d.Passivation film 27 is formed between interlayer insulation film 34, TFT10, and TFT 11.

Electric conduction oxide film 28 is layered on passivation film. Thirdmetal layer 29 is layered on electric conduction oxide film 28. Gatewiring 7 and relaying electrode 31 are formed in third metal layer 29.As discussed later, gate wiring 7 and relaying electrode 31 are formedfrom the metal of third metal layer 29. Electric conduction oxide film28 is formed selectively on an area overlapping with gate wiring 7 andrelaying electrode 31. The area overlapping with gate wiring 7 and thearea overlapping with relaying electrode 31 are not electricallyconnected.

Gate insulation film 23 and passivation film 27 have a contact hole 32penetrating the films in a thickness direction at where the films 23 and27 overlap with gate wiring 7 and gate electrode 10 g. Gate wiring 7 isconnected electrically to gate electrode 10 g formed in first metallayer 22, via the contact hole 32. Gate wiring 7 and gate electrode 10 gdo not directly contact each other because electric conduction oxidefilm 28 is intervened between them.

Similarly, passivation film 27 has a contact hole 33 penetrating thefilm 27 in a thickness direction at where the film 27 overlaps withsource electrode 11 s of TFT 11 and relay electrode 31. Relay electrode31 is connected electrically to source electrode 11 s formed in secondmetal layer 26, via the contact hole 33. Source electrode 11 s and relayelectrode 31 are not directly contacted each other because electricconduction oxide film 28 is formed between them.

Interlayer insulation film 34 is formed on passivation film 27 and thirdmetal layer 29 such that the film 34 covers gate wiring 7 and relayelectrode 31. The film 34 has a layered structure and comprisesinterlayer insulation film 34 a working as a planarization film, andinterlayer insulation film 34 b working as a passivation film. The film34 a is made of organic material film or hybrid film and is formed onthe upper side layer which contacts the anode 2. The film 34 b is madeof inorganic film and is formed on the lower side layer which contactsgate wiring 7 and relay electrode 31.

Bank 5 a is formed on interlayer insulation film 34 in a portion thatborders with neighboring pixel 5. In the opening of bank 5 a, anode 2and EL layer 3 are formed. One anode 2 is formed for one pixel 5. One ELlayer 3 is formed for one color (one sub pixel column) or for one subpixel. The transparent cathode 4 is formed on EL layers 3 and banks 5 a.

As illustrated in FIG.6, interlayer insulation film 34 has a contacthole 35 penetrating the film 34 at where the film 34 overlaps with anode2 and relay electrode 31. Anode 2 is connected electrically to relayelectrode 31 formed in third metal layer 29, via the contact hole 35.Relay electrode 31 comprises: center area 31 a that fills in contacthole 33, and flat area 31 b which extends at the upper portion of thecontact hole 33. Anode 2 is connected electrically on flat area 31 b ofrelay electrode 31.

In the present disclosure, anode 2 of the luminescence unit is made of aconductive metal material comprising essentially aluminum. Relayelectrode 31 for supplying current to TFT array unit 1 is made ofconductive metal material including Cu (copper) which is different fromthe material of anode 2. On the boundary face of anode 2 and relayelectrode 31, diffusion-prevention film 36 is formed.Diffusion-prevention film 36 is made of metal oxide comprisingessentially aluminum, which is the same material with anode 2 of theluminescence unit. Material composition of diffusion-prevention film 36is AlxCuyOz, which satisfies x>y≧0, and z>0, when measured by EnergyDispersive X-ray Spectrometer (EDS), for example.

Table 1 shows characteristics of above mentioned diffusion-preventionfilm 36, which is formed between an aluminum-based anode 2 and acopper-based relay electrode 31. Here, four kinds of samples havingdifferent film thickness of diffusion-prevention film 36, i.e. Examples1 to 4 of the present disclosure, and comparative samples (ComparativeExamples 1 to 3) are prepared. Then the amount of contact defect andcounter diffusion between anode 2 and relay electrode 31 are comparedfor each of the samples.

Regarding to contact defect, samples having connection resistance lessthan 1 kilo-omega per unit area are indicated as non-defective samples(letter “o”) and samples having connection resistance equal to or morethan 1 kilo-omega per unit area are indicated as defective samples(letter “x”) in Table 1. Regarding to counter diffusion amount,inventors have confirmed from an experiment that when this amount isless than 100 nano-meters, counter diffusion of aluminum and copperhardly causes electro-migration and disconnection. Accordingly, thesamples having the amount less than 100 nano-meters are indicated asnon-defective samples (letter “o”) and the samples having the amountequal to or more than 100 nano-meters are indicated as defective samples(letter “x”).

TABLE 1 Film Thickess Contact Counter Diffusion (nm) Defect AmountExample 1 1 O O Example 2 2 O O Example 3 4 O O Example 4 6 O OComparative Example 1 8 X O Comparative Example 2 9 X O ComparativeExample 3 10 X O

According to the result shown in Table 1, non-defective sample, havingsmall contact defect and counter diffusion, can be obtained when filmthickness t of the diffusion-prevention film 36 is between 1 to 6nano-meters. Film thickness t of diffusion-prevention film 36 can bepreferably 0<t≦6 nano-meters, because contact resistance can be madelower when film thickness t of diffusion-prevention film 36 is smaller,and thus have an advantageous electrical property. However, the counterdiffusion of aluminum and copper may likely to occur due tothermal-history during a manufacturing process after the formation ofdiffusion-prevention film 36. Considering the variation in themanufacturing process, thickness of diffusion-prevention film 36 isdesirably between 1 to 6 nano-meters.

Diffusion-prevention film 36 having thin film thickness can befabricated by first forming contact hole 35 by dry etching, and thenforming anode 2 using sputtering method in a vacuum continuously withoutbeing exposing to the room air. The film thickness ofdiffusion-prevention film 36 can be controlled by adjusting the filmthickness of a copper-based oxide film before forming anode 2. The filmthickness of the oxide film can be controlled first by forming an oxidefilm, and then by removing the oxide film physically using Ar (argon)plasma or reduction process using H2 plasma, for example.

As discussed above, the present disclosure relates todiffusion-prevention film 36 made of aluminum-based oxide. The film 36is formed between anode 2 made of aluminum-based conductive material andrelay electrode 31 made of conductive material including copper which isa material different from that of anode 2. The electro-migrationoriented disconnection due to counter diffusion of aluminum and coppercan thereby be prevented. Further, a sufficient contact characteristiccan be acquired by adjusting the film thickness of diffusion-preventionfilm 36 between 1 to 6 nano-meters, and disconnection due to counterdiffusion is also prevented.

Next, manufacturing process of TFT array unit 1 according to anexemplary embodiment is discussed with reference to FIGS. 7A to 7F, andFIGS. 8A to 8H.

Substrate 21 is prepared first as shown in FIGS. 7A and 8A. Generally,an insulating material, such as glass and quartz are used for substrate21. An oxidization silicon film or a silicon nitride film can be formedon the upper surface of substrate 21 to prevent impurity diffusion fromsubstrate 21. The film thickness is about 100 nm.

Next, as shown in FIGS. 7B and 8B, first metal layer 22 having heatresistance is formed on substrate 21. Gate electrodes 10 g and 11 g arethen formed by patterning using photo-lithographic method or etchingmethod etc. The electrodes can be made of a heat resistant material suchas Mo (molybdenum), W (tungsten), Ta (tantalum), Ti (titanium), and Ni(nickel); or alloy thereof. In the present example, Mo is used.Desirably, the thickness is 100 nano-meters.

Next, as shown in FIGS. 7C and 8C, gate insulation film 23 is formed onsubstrate 21 and first metal layer 22. Then, semiconductor layers 24 and25 are formed on gate insulation film 23. Gate insulation film 23 andsemiconductor layers 24 and 25 are formed continuously in a vacuum stateusing plasma CVD method etc. Gate insulation film 23 is made of anoxidization silicon film, a silicon nitride film, or composite membranethereof. Thickness is about 200 nano-meters. Semiconductor layers 24 and25 are made of amorphous silicon films with thickness of about 50nano-meters.

Then, an excimer-laser is irradiated on semiconductor layer 25 asillustrated in arrows of FIG. 8D, to change the property ofsemiconductor layer 25 from a non-crystalline semiconductor layer to amulti-crystalline semiconductor layer. The crystallization here can beachieved by first dehydrate in an oven of temperature between 400Celsius and 500 Celsius, then crystallize using an excimer laser, andperform hydrogen plasma processing thereafter in a vacuum for severalseconds to several tens of seconds. Specifically, temperature of thenon-crystalline semiconductor layer is raised to a predeterminedtemperature range by irradiating with the excimer laser. Here, thepredetermined temperature range is 210 to 1414 Celsius, for example. Theaverage diameter of crystal grain of the multi-crystalline semiconductorlayer is between 20 to 60 nano-meters.

First metal layer 22, which constitutes gate electrodes 10 g and 11 g,needs to be formed by a metal having melting temperature higher than theupper limit of the temperature range (i.e. 1414 Celsius) because thelayer 22 is exposed to a high temperature in the above-mentionedprocess. On the contrary, second metal layer 26 and third metal layer29, which will be layered in the subsequent processes, can be formed ofmetal having a melting temperature lower than the lower limit of thetemperature range (i.e. 210 Celsius).

Next, as illustrated in FIG. 8E, semiconductor layer 25 is formed intoan island-like semiconductor layer using photo-lithographic method oretching method etc. The contact hole 30 is also formed in gateinsulation film 23 by the photo-lithographic method or etching methodetc.

Thereafter, as illustrated in FIGS. 7D and 8F, second metal layer 26 isformed on gate insulation film 23, semiconductor layer 24 (notillustrated in FIGS. 7D or 8F) and semiconductor layer 25. Source wiring8, power supply wiring 9, source electrodes lOs and 11 s, drainelectrodes 10 d and 11 d, and relay electrode 31 is then fabricatedrespectively by patterning. At this point, material constituting secondmetal layer 26 is also filled in contact hole 30 to form metal filledcontact hole 30. By this process, gate electrode 11 g and drainelectrode 10 d are electrically connected via contact hole 30 as shownin FIG. 4. Second metal layer 26 can be made of low resistance metalssuch as Al (aluminum), Cu (copper), and Ag (silver) or an alloy thereof.In this embodiment, Cu is used and the thickness is about 300nano-meters.

Generally, a semiconductor layer of low resistance is formed betweensource electrode 10 s and semiconductor layer 24 and also between drainelectrode 10 d and semiconductor layer 24. This low resistancesemiconductor layer is generally made of an amorphous silicon layer towhich n-type dopant such as phosphorus is doped, and of an amorphoussilicon layer to which p-type dopant such as boron is doped. Thethickness is about 20 nano-meters. An amorphous silicon layer can befurther formed between the crystallized semiconductor layer 24 and thedoped amorphous silicon layer. These films may be necessary forimproving the device property. The similar structure can be applied tosemiconductor layer 25.

Then as shown in FIGS. 7E, 7F, and 8G, passivation film 27 is formed ongate insulation film 23, semiconductor layer 24 (not illustrated),semiconductor layer 25, and second metal layer 26. Passivation film 27can made of an oxidization silicon film, a silicon nitride film, orlayered films thereof. Using photo-lithographic method or etchingmethod, contact hole 32 that penetrates gate insulation film 23 andpassivation film 27 continuously, and contact hole 33 that penetratespassivation film 27 in the thickness direction are formed in passivationfilm 27.

The material and film thickness of gate insulation film 23 which isinserted between first metal layer 22 and second metal layer 26, andpassivation film 27 which is inserted between second metal layer 26 andthird metal layer 29 are determined such that the capacity per unit areaof passivation film 27 becomes larger than that of gate insulation film23. The capacity per unit area of passivation film 27 is preferably lessthan 1.5*10⁻⁴ (F/m²). The capacity per unit area of gate insulation film23 is preferably equal to or more than 1.5*10⁻⁴ (F/m²).

Then, as illustrated in FIGS. 6 and 8H, electric conduction oxide film28 is formed on passivation film 27 and third metal layer 29 is formedon electric conduction oxide film 28. Third metal layer 29 is fabricatedinto gate wiring 7 and relay electrode 31 by patterning. Electricconduction oxide film 28 can be made of an oxide film including indiumand tin or of an oxide film including indium and zinc. Third metal layer29 can be made of a material having low resistance, for example thematerial same as second metal layer 26. In the present disclosure, amaterial including copper (Cu) is desirable. Thickness is about 300 nm.

At this point, metal filled contact holes 32 and 33 are formed byfilling a material constituting electric conduction oxide film 28 andthird metal layer 29 in the contact holes 32 and 33. Gate wiring 7 andgate electrode 10 g are thereby connected electrically via the contacthole 32. Source electrode 11 s and relay electrode 31 are connectedelectrically via the contact hole 33.

Next, forming process of area A of FIG. 6 is detailed with reference toFIGS. 9A to 9G. Specifically, fabrication of connection unit of relayelectrode 31 and anode 2 using self-alignment is discussed.

First, the structure illustrated in FIG. 9A is formed throughmanufacturing processes of FIGS. 8A to 8H discussed above.

As illustrated in FIG. 9B, interlayer insulation film 34 b is formed onpassivation film 27 and relay electrode 31. Interlayer insulation film34 b is formed using plasma CVD method etc. Interlayer insulation film34 b can be made of an oxidization silicon film, a silicon nitride film,or composite films thereof. The thickness of the film 34 b is about 200nano-meters and this film functions as a passivation film.

Next, as illustrated in FIG. 9C, interlayer insulation film 34 a isformed on interlayer insulation film 34 b. Interlayer insulation film 34a functions as planarizing film and preferably made of coating materialwhich can have a substantial thickness, such as spin coater and slitcoater. Interlayer insulation film 34 a is preferably a photosensitivematerial, and can be made of an organic material such as acrylic resinand polyimide resin, or hybrid materials such as SOG (Spin-On Glass)material having Si—O connection. Thickness of the film 34 a is about4000 nano-meters.

Next, as illustrated in FIG. 9D, interlayer insulation film 34 a, whichis a photosensitive material, is fabricated using photo-lithographicmethod to form a contact hole 35 that penetrates interlayer insulationfilm 34 a. Interlayer insulation film 34 a made of coated material iscured by baking at about 230 Celsius. Interlayer insulation film 34 bmade of an inorganic film prevents relay electrode 31 from corrosion dueto a gas, such as moisture generated from interlayer insulation film 34a during the baking of the film 34 a.

Next, a forming process of diffusion-prevention film 36 is discussedwith reference to FIGS. 9E to 9G.

First, using a patterned contact hole 35 as a mask, interlayerinsulation film 34 b is fabricated by dry etching such that the contacthole 35 penetrates the film 34 b, as illustrated in FIG. 9E.

Next, as illustrated in FIG. 9F, a copper-based oxide film 31 a isformed on relay electrode 31 which is in e contact hole 35. Asillustrated in FIG. 9G, contact hole 35 is filled with a material sameas that of anode 2. Anode 2 and relay electrode 31 are connectedelectrically via this contact hole 35. Anode 2 can be made of conductivemetal, such as Mo, Al, Ag, Au, and Cu, or alloy thereof. Anode 2 can bealso made of an organic conductivity material, such as PEDOT/PSS or ofzinc oxide, zinc-added indium oxide. Among them, Al-based metal ispreferable for anode 2 because the reflectivity is high and cost is low.An electrode pattern is formed by forming a layer using vacuumevaporation method, electron beam evaporation method, RF sputteringmethod, or printing method.

As a result of the above process, Cu-based oxide film 31 a and Al-basedanode 2 is connected. However, Al-based diffusion-prevention film 36 isformed because Al has tendency to become ion compared to Cu. A bakingprocess can be added to accelerate an oxidation-reduction reaction.

Among the above-mentioned manufacturing process, the process of FIGS. 9Eto 9G can be done by self-alignment using interlayer insulation film 34a as a mask. Accordingly, the influence of chemical solution during thephoto-resist removal can thereby be avoided, and the use of mask iseliminated, which simplifies manufacturing process and reducesmanufacturing cost.

Subsequent to the formation of anode 2 illustrated in FIG. 9G, the ELdisplay is manufactured by layering bank 5 a, EL layer 3, and thetransparent cathode 4 on TFT array unit 1 in sequence.

Specifically, banks 5 a are formed first on interlayer insulation film34 in positions corresponding to boundaries of each pixels 5. EL layer 3is formed on anode 2 and in opening of bank 5 a for every color, i.e.sub pixel column, or for every sub pixel. This EL layer 3 is configuredby a layered structure of an electron hole injection layer, an electronhole transportation layer, a luminescence layer, an electrontransportation layer, and an electron injection layer. Copperphthalocyanine can be employed as the electron hole injection layer.Naphthyl diamine, i.e. —NPD (Bis[N-(1-Naphthyl)-N-Phenyl]benzidine) canbe employed as the electron hole transportation layer.Tris(8-hydroxyquinolinato) aluminum, i.e. Alq3 (tris(8-hydroxyquinoline)aluminum)) can be employed as the luminescence layer. Oxazole derivativecan be employed as the electron transportation layer. Alq3 can beemployed as the electron injection layer. However, these materials arethe examples and other materials can be employed.

Transparent cathode 4 is an electrode having permeableness and is formedcontinuously on EL layer 3. Transparent cathode 4 can be made of ITO,SnO₂, In₂O₃, or ZnO. Transparent cathode 4 can be also made ofcombination of these materials.

In the above embodiment, the number of the TFTs constituting pixel 5 istwo; however three TFTs can be employed to compensate the dispersionbetween the TFTs of pixel 5. In this case, the similar structure can beemployed. In the above embodiment, pixel structure for driving anorganic EL device is discussed; however, the present disclosure can beapplied to TFT arrays used for LCD displays or inorganic EL displays.

As described above, the EL display of this embodiment has a luminescenceunit having a luminescence layer disposed between a pair of electrodesand TFT array unit 1 that controls the light emission of theluminescence unit. An interlayer insulation film is disposed between theluminescence unit and a TFT array unit 1. One of the electrodes of theluminescence unit is connected electrically with TFT array unit 1 viacontact hole of the interlayer insulation film. TFT array unit 1 has acurrent-supplying-electrode that is connected electrically to theelectrode of the luminescence unit via the contact hole of theinterlayer insulation film. Diffusion-prevention film 36 is formed atthe interface of the electrode of the luminescence part and the currentsupplying electrode of TFT array unit 1.

The foregoing structure allows sufficient contact characteristics, andcan avoid disconnection due to counter diffusion.

INDUSTRIAL APPLICABILITY

The present disclosure is useful for improving characteristic of TFTarray unit used for EL display.

The invention claimed is:
 1. An EL display comprising: a luminescenceunit having a luminescence layer disposed between a pair of electrodes;a thin film transistor array unit controlling luminescence of theluminescence unit; an interlayer insulation film disposed between theluminescence unit and the transistor array unit; and a current supplyingelectrode connected electrically to an electrode of the luminescenceunit and for connecting the electrode of the luminescence unit to thethin film transistor array unit via a contact hole of the interlayerinsulation film, wherein a diffusion prevention film is formed on aboundary face between the electrode of the luminescence unit and thecurrent supplying electrode, and the diffusion prevention film is madeof an oxide having a main component same as material constituting theelectrode of the luminescence unit, and the diffusion prevention filmhas a material composition of Al_(x)Cu_(y)O_(z) where x>y≧0, and z>0. 2.The EL display of claim 1, wherein the diffusion prevention film has afilm thickness t, where 0<t≦6 nano-meters.
 3. A thin film transistorarray unit having an interlayer insulation film disposed between aluminescence unit and a current supplying electrode connectedelectrically to an electrode of the luminescence unit via a contact holeof the interlayer insulation film, wherein a diffusion prevention filmis formed on a boundary face between the electrode of the luminescenceunit and the current supplying electrode, and the diffusion preventionfilm is made of an oxide having a main component same as materialconstituting the electrode of the luminescence unit, and the diffusionprevention film has a material composition of Al_(x)Cu_(y)O_(z) wherex>y≧0, and z>0.
 4. The thin film transistor array unit of claim 3,wherein the diffusion prevention film has a film thickness t, where0<t≦6 nano-meters.